View full sizeNorovirus outbreaks in restaurants are relatively rare but Andina, a high-end Peruvian restaurant in the Pearl District, has had two norovirus outbreaks in a year.Bruce Ely/The Oregonian

The norovirus outbreak traced to Andina restaurant this month was just the latest that Multnomah County health officials have investigated countywide in recent months.

The county, and the state, have seen a spike in norovirus cases this winter, the bug's high season.

Amy Sullivan, head of the county's communicable disease program, said the virus is pervasive. "It can happen in your home," Sullivan said. "It can happen in school. It can happen everywhere."

Norovirus strikes the highest numbers in nursing homes, according to state statistics, followed by child care centers, schools and hospitals, in that order.

Outbreaks traced to restaurants are relatively rare. Excluding the latest one at Andina earlier this month, Multnomah County has had 47 norovirus outbreaks in the past two years. Four were caused by restaurants. Andina was one.

Last April, six people developed gastrointestinal symptoms after eating at the restaurant, a high-end establishment in the Pearl District. The county sent an inspector to look for sanitation problems.

That visit did not turn up any red flags, according to Christie Sweitz, head of the county’s restaurant inspections. Officials inspected the restaurant again last June and in August, then visited earlier this month in connection with the latest outbreak that has sickened more than 30.

Emilio DeBess, a state epidemiologist, said Andina staff threw out all suspect food after learning about the latest outbreak and replaced a refrigeration unit to guard against bacterial contamination. He said staff also appeared to be practicing proper sanitation.

Norovirus is a hardy bug. Passed directly among people or indirectly through food, water or surfaces, it can live six weeks outside the body. It survives in cold and is killed only at 140 degrees Fahrenheit. That's why health officials emphasize that sick people should stay home and that food handlers should thoroughly wash their hands and preparation surfaces for at least 20 seconds with hot, soapy water.

The county does not alert the public unless it considers the outbreak a public health threat.

"Usually when we hear about these things they're over," Sullivan said. "People get better in two days."

But sometimes they don't. The Centers for Disease Control and Prevention reports that norovirus kills 800 people a year in the United States and hospitalizes 70,000.